I've been poking at this question intermittently ... and I'm stumbling in finding a definitive source 'knowledge base' article.
Still, at the moment, it seems to me that the N5K has a unique feature here, the ability to shield ingress (source) traffic from the contention induced by a SPAN port.
I don't see a similar feature on the C4K or C6K, for example (i.e. rate-limiting SPAN ports).
In thinking about this, it seems to me that one needs to understand the architecture of the switch in order to assess the potential for impacting source traffic. So, for example, if one is SPANning a port on a typical C4K line card (8 10/100/1000 ports sharing a single 1Gps uplink to the Sup card) *and* one is mirroring to another member of the same 8 port group, then it seems like to me that the source port would discard frames, assuming that the source port is pushing past 50% of that 1 Gps uplink.
That being said, I have a buddy who believes the C6K is fairly immune to this effect, on account of some aspect of its switching design.
Am I on the right track here, in terms of figuring out (a) how to assess potential impact to source traffic, and (b) in claiming that only the N5K has this SPAN rate-limiting command?
Before I go leaving sniffers SPANning 10Gb/s ports for long periods of time, I want to understand the risk of impacting production traffic.
--sk